The invention relates to methods and apparatus for producing submicron patterns on films. This invention was made with government support under NSF #DMR-9809365. and DOE #DE-FG02-96ER45612. The government has certain rights in this invention.
In the microelectronics, biotechnology, adhesive, and microsystem industries, it is important to produce high-resolution patterns on substrates. For examples, such high-resolution patterns are necessary to produce integrated circuits. Limits on the resolution of such patterns limit the performance of such integrated circuits. Presently, microlithography is commonly used to produce patterns on substrates. Microlithography techniques involve exposing a photoresist to an optical pattern, and using chemicals to etch either the exposed. or unexposed, portions of the photoresist to produce the pattern on the substrate. The resolution of the pattern is thus limited by the wavelength of light used to produce the optical pattern.
The present invention relates to a technique for producing lithographic structures by exposing at least one film on a substrate to an externally applied electric field, such as that produced within a parallel plate capacitor. The externally applied electric field produces forces in the film that cause mass transfer in the film to thereby produce a lithographic pattern. The resolution of the pattern will depend on the magnitude of the electric field, and the dielectric constant, surface energy, and the viscosity of the film. The pattern can be further specified by spatially controlling the electric field, e.g., by using patterned electrodes in the capacitor. The pattern can also be further specified by spatially varying the surface energy of the film.
In general, in one aspect, the invention features a method for forming a patterned film on a substrate. The method includes providing a first flowable medium on the substrate and a second flowable medium on the first flowable medium. The first and second flowable media have different dielectric properties and define an interface between them. The method further includes applying an electric field to the interface for a time sufficient to produce a structure in the first flowable medium along the interface, and hardening the structure in the first flowable medium to form the patterned film.
Embodiments of the invention can include any of the following features.
For example, the first flowable medium can be a liquid, and the second flowable medium can be another liquid, or a gas at any pressure. Furthermore, the hardening can include: initiating a chemical reaction in the first flowable medium; polymerizing the first flowable medium; or cross-linking the first flowable medium.
To create a selected pattern, the application of the electric field can include laterally varying the strength of the electric field along the interface to define the structure. Furthermore, the method can include providing the substrate with a laterally varying surface energy to further define the structure. Alternatively, the method can include providing the substrate with a laterally varying surface energy to further define the structure, without laterally varying the strength of the electric field along the interface.
The substrate can include a lower electrode and the application of the electric field can include applying a voltage across the lower electrode and an upper electrode spaced from the lower electrode by at least the first and second flowable media. Furthermore, to laterally vary the strength of the electric field along the interface, the method can involve any of the following: at least one of the upper and lower electrodes can have a topography that defines a laterally varying separation between the electrodes; at least one of the upper and lower electrodes can include multiple, lateral regions having different conductivities; and the substrate can include a layer of non-conductive material positioned between the lower electrode and the first flowable medium, wherein the layer of non-conductive material includes multiple, lateral regions having different dielectric properties. Moreover, the substrate can include multiple, independently addressable lower electrodes and/or there can be multiple, independently addressable upper electrodes, to thereby laterally vary the strength of the electric field along the interface. For example, the application of the external electric field can include generating multiple, potential differences between one or more of the lower electrodes and one or more of the upper electrodes.
More generally, when the substrate includes a lower electrode, the substrate can include a layer of non-conductive material positioned between the lower electrode and the first flowable medium. Furthermore, the upper electrode can be spaced from the second flowable medium by a layer of non-conductive material. That layer of non-conductive material may include multiple, lateral regions having different dielectric properties, to laterally vary the strength of the electric field along the interface.
The method can further include separating the upper electrode and the second flowable medium from the hardened lateral structure to reveal the patterned film. Also, the method can be repeated to form multiple patterned films on the substrate.
Furthermore, the method can be used for microlithography. For example, the patterned film can expose selected regions of the substrate and the method can further include removing a layer of the substrate at each of the exposed regions. Also, the patterned film can expose selected regions of the substrate and the method can further include depositing a layer of material at each of the exposed regions of the substrate.
In another aspect, the invention features the patterned film produced by the method.
In general, in another aspect, the invention features a method for producing a pattern on multiple substrates. Each of the multiple substrates has at least one lower electrode. The method includes: providing a master defining the pattern, the master including at least one upper electrode; providing a first flowable medium on one of the substrates; positioning the master above the first flowable medium spaced from the first flowable medium by at least a second flowable medium, the first and second flowable media having different dielectric properties and defining an interface there between; applying a voltage across at least one of the lower electrodes and at least one of the upper electrodes for a time sufficient to produce a structure in the first flowable medium along the interface; hardening the lateral structure in the first flowable medium to form the pattern; and using the same master, repeating the second providing step, the positioning step, the generating step, and the hardening step for additional ones of the substrates.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
The techniques disclosed herein can include many advantages. For example, the patterns are produced without optical radiation, and therefore their resolution is not limited by the wavelength of optical radiation. In principle, the lateral resolution of the pattern can be made arbitrarily small by controlling the externally applied electric field and selecting a film with appropriate properties. Furthermore, the techniques can produce high-resolution patterns on the film, without requiring the use of chemicals to etch or remove portions of the film.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.